One star collides with the other and falls into the shadow, hiding its light from the renewed light.
This directly alludes to Stephen colliding with Matilda until she falls into the alluded shadows when she returns back to Normandy. The renewed light one might assume is Stephen after his release. It could possibly be Henry II, but I doubt Henry Blois would view King Henry’s reign as renewed light. Matilda’s forces defeated and captured King Stephen at the Battle of Lincoln in February 1141. He became a prisoner in her brother’s castle. When she arrived in London, the city was ready to welcome her and support her coronation. As the Gesta Stephani relates she used the title of Lady of the English and planned to assume the crown.
However, she refused the request of the citizens of London to reduce their taxes. Because of her own arrogance and Henry Blois’ underhanded dealings and change of allegiance (due to Queen Matilda’s petitions to him to aid in the release King Stephen)…. the Empress had to flee the city of London. Stephen was eventually freed and exchanged for Robert of Gloucester who was captured at the rout of Winchester in September of 1141 while facilitating his sister’s escape.
At the death of Eustace, Stephen’s son, Henry Fitz Empress and Stephen ratified the terms of a permanent peace. Stephen announced the Treaty of Winchester in Winchester Cathedral: he recognized Henry Plantagenet as his adopted son and successor, in return for Henry doing homage to him. King Stephen promised to listen to Duke Henry’s advice, but retained all his royal powers. Stephen’s remaining son, William, would do homage to Duke Henry and renounce his claim to the throne, in exchange for promises of the security of his lands.
However, earlier in 1148, Matilda and Henry Fitz Empress had returned to Normandy, following the death of Robert of Gloucester, and the re-conquest of Normandy by Geoffrey of Anjou. Upon their arrival, Geoffrey turned Normandy over to his son Henry Fitz Empress and retired to Anjou. Henry Plantagenet assumed the title Duke of Normandy, and Matilda became Duchess of Normandy and retired to Rouen for her remaining years, where she maintained her own court and presided over the government of the duchy for her son who then ultimately became Henry II of England.